The invention relates to a device for holding a projectile in relation to the casing of a telescoped ammunition round wherein the projectile is confined to the cartridge case.
Telescoped ammunition which have given rise to many developments in the last few years, are characterized in that the projectile is disposed inside the cartridge casing containing the propelling charge instead of protruding outside the latter.
The main advantage of such an arrangement is that, it makes it possible to define shorter ammunition rounds, which enables more compact or higher-rate-of-fire weapons to be designed.
However, in developing of such ammunition rounds, to a number of difficulties arise.
For example, the projectile is not introduced into the weapon barrel when the round is disposed in the chamber and it is the pressure due to the combustion of the grain charge gases which first introduces the projectile into the barrel.
In order to obtain the same ballistic performance as that of a conventional round, it is desirable to fill the cartridge case of the round with the greatest possible quantity of propellent powder, which imposes the presence of an annular layer of this powder around the projectile.
Upon ignition, it is to be feared that the combustion gases will precede the projectile before the latter has entered into the barrel deeply enough to ensure gas-tightness.
Various solutions have been envisaged to avoid this phenomenon; as an example, U.S. Pat. No. 4,604,954 describes an ammunition round wherein a first grain charge, contained in a small cylinder, acts only upon the projectile through a piston sliding in this cylinder; the main grain charge surrounding the projectile is ignited only when the latter has entered into the weapon barrel.
Such an ammunition round is complex because it requires the assembly of several parts of fine mechanics; moreover, the transition between the combustion of the first grain charge and that of the second grain charge is difficult to control, which may reduce the efficiency of the propellent charge, and thus the performance of the ammunition round.
U.S. Pat. No. 4,770,098 proposes an ammunition round wherein a sleeve closes the fore section of the cartridge casing, this sleeve of plastic material includes a hole the diameter of which is slightly smaller than that of the projectile.
So, the projectile is immobilized by the sleeve thus providing gas tightness for gases from the combustion of the propellin charge.
The sleeve also permits placement of the projectile in relation to the cartridge casing, thus also to the weapon barrel; a number of holes permit variance of the sleeve stiffness and thus the minimum pressure required for setting the projectile in motion.
Such a concept of ammunition round is particularly interesting because it makes it possible to produce telescoped ammunition with a single propelling charge.
However, the sleeve is not sufficient for holding the projectile and, therefore, the inner surface of the cartridge casing includes axial ribs intended to support the aft section of the projectile.
These ribs reduce the volume available for the powder and may disturb the ignition regularity.
It might seem advantageous to suppress the ribs, but this would require the use of a sleeve with a large surface of contact with the projectile, a solution which is not acceptable because a long sleeve reduce the volume available for the powder.
GB patent 1310607 shows a telescoped ammunition round comprising a casing fitted with radial ribs which support the projectile, and a plug which provides for gas-tightness and ensures a maximum axial holding of the projectile in relation to the casing.
This arrangement present the same disadvantages as that of U.S. Pat. No. 4,770,098 (i.e., the ribs support the projectile radially but limit the volume available for the propelling charge).
U.S. Pat. No. 3,575,112 describes a compact ammunition round comprising a plurality of molded propelling charge elements.
The projectile is disposed in a hole of this solid charge and is supported radially by the solid charge; a washer provides for the axial positioning of the projectile and is glued to the propelling charge.
The washer is not integral with the projectile, which implies that, in case of a break in the propellent grains due to mechanical stresses during projectile introduction into the weapon barrel, the projectile will not be supported radially.
This arrangement is inconvenient since the ammunition round does not include a casing containing the grain charge and the washer is glued on the charge itself which runs the risk of breaking.
U.S. Pat. No. 4,015,527 shows an amunition round also comprising a plurality of molded propelling charges disposed within a combustible casing which is not closed by a sleeve.
The object of the invention is to propose a device for holding a projectile in relation to the casing of a telescoped ammunition round which does not present such disadvantages.